A power battery is responsible for storing and supplying electric energy. In use, it is necessary to design an insulation detection circuit to monitor in real time whether an insulation resistance of an entire high voltage system of an electric vehicle (including the insulation resistance of a power battery pack and the entire vehicle) meets a standard, so as to avoid high voltage safety issues caused in the case that the insulation resistance of the high voltage system of the electric vehicle does not meet the standard.
In order to detect the insulation resistance of the power battery, a conventional insulation detection circuit needs to directly inject a high-frequency AC (Alternating Current) signal into the power battery, connect one end of the high-frequency AC signal to the ground or a body of the vehicle, and then calculate the insulation resistance according to acquired signals.
However, inventors of the present application found that when using the existing method of injecting the high-frequency signal, the detection result of the insulation resistance is usually impacted by a parasitic capacitance of the power battery under detection, resulting in a large detection error of the insulation resistance.